In Part I of this series, I outlined some of the sure signs that your computer is infected with a virus. However, sometimes identifying a virus is not so cut and dry as the symptoms can disguise themselves as Windows problems.

You might have a virus if…

A virus infection could also cause some of the following symptoms. Keep in mind that these symptoms are also typical of ordinary Windows system problems, so they cannot be definitively viral symptoms without running a complete virus scan with updated definitions.

• Windows will not start at all, even though the user has made no system changes, installed or removed any programs, or made any Registry edits since the last time it started successfully.
• Windows will not start because certain critical system files are missing (and you see an error message listing those files), and the user is confident that he or she did not accidentally delete them.
• The PC starts up normally sometimes, but at other times will hang before the desktop icons and taskbar appear.
• The PC runs very slowly and/or takes a long time to start up.
• Out-of-memory error messages appear, even though the PC has plenty of RAM.
• Viewing the system processes via Task Manager shows that an unknown process is consuming a high percentage of the CPU time.
• From the Task Manager view, you notice programs or processes running that you do not recognize, even after shutting down all running programs and system tray utilities.
• New applications will not install properly.
• Windows spontaneously reboots for no apparent reason.
• Applications that used to run normally are now crashing frequently. Removing and reinstalling them does not solve the problem.
• A disk utility such as Scandisk reports multiple serious disk errors.
• A partition completely disappears.

The key to distinguishing virus-related system problems from ordinary ones is often situational. What did the user do right before the problem started? It never hurts to ask. If possible, check the user’s e-mail box to see whether an e-mail containing a virus might still be hanging around there. Check his or her Deleted Items and Sent Items folders as well to see if the virus may have been spread to others.